1. Field of the Invention
The present invention relates to a switching/moving structure of a zoom lens.
2. Description of the Related Art
A lens barrel, wherein a linear guide ring which is supported to be linearly movable along an optical axis without rotating and a rotatable ring are coupled in a first bayonet manner at a predetermined relative rotational position between the linear guide ring and the rotatable ring so that the rotatable ring is freely rotatable relative to the linear guide ring and so that the rotatable ring and the linear guide ring are immovable relative to each other along the optical axis and further wherein a moving frame (lens group support ring) which is supported by the linear guide ring to be linearly movable along the optical axis without rotating and a switching ring which rotates together with the rotatable ring and which is movable relative to the rotatable ring along the optical axis are coupled in a second bayonet manner at a predetermined relative rotational position between the moving frame and the switching ring so that the switching ring is freely rotatable relative to the moving frame and so that the switching ring and the moving frame are immovable relative to each other along the optical axis, is known in the art. The moving frame is provided on an outer peripheral surface thereof with a male helicoid while the rotatable ring is provided on an inner peripheral surface thereof with a female helicoid which is engaged with the male helicoid of the moving frame. A rotation of the rotatable ring causes the moving frame (which supports the first lens group) to move linearly along the optical axis due to engagement of the male helicoid of the moving frame with the female helicoid of the rotatable ring, and further causes lens groups positioned behind the first lens group to move along the optical axis by motion of the cam formed on the rotatable ring.
In addition to the above described structure of the known lens barrel, a zoom lens barrel which is currently under development by the assignee of the present invention includes a structure in which a switching leaf is supported by the linear guide ring to be freely movable in a circumferential direction of the linear guide ring within a predetermined range of movement without moving along the optical axis relative to the linear guide ring while a switching-member moving groove is formed on an inner peripheral surface of the switching ring to be engaged with a follower projection which projects from the switching leaf so that the distance between the second lens group and the third lens group varies by a movement of the switching leaf in a circumferential direction of the linear guide ring. The switching-member moving groove includes a first inclined section (telephoto section), a switching section, and a second inclined section (wide-angle section) in that order from rear to front of the zoom lens barrel. The first inclined section is shaped so that the lead angle thereof is the same as that of the threads of the female helicoid of the rotatable ring and so that the direction of inclination of the first inclined section is opposite to that of the threads of the female helicoid of the rotatable ring. The switching section is shaped to extend parallel to the optical axis from the front end of the first inclined section, and wherein the second inclined section is shaped to extend parallel to the first inclined section from the front end of the switching section.
However, in this zoom lens barrel which is currently under development, it has been proved that neither making the linear guide ring and the rotatable ring coupled in the aforementioned first bayonet manner nor making the moving frame the switching ring coupled in the aforementioned second bayonet manner is possible, and that neither making the moving frame and the rotatable ring coupled in a helicoid manner (i.e., via the aforementioned male and female helicoids) is possible.